Optical transmission element

ABSTRACT

Between an optical fiber (LF 11 , LFB 12 , LFB 13 ) and a surrounding core covering (AH 11 , AH 12 , SB 13 ) of an optical transmission element (OE 11  to OE 13 ) there is at least one dry and compressible fixating element (FE 11  to FE 13 ), which surrounds the optical fiber totally or partially, and which exerts a defined contact pressure against the core covering and against the optical fiber for fixating the optical fiber in the longitudinal direction of the transmission element. The fixating element is further formed and positioned in such a way, that position changes of the optical fiber due to bending or elongation are possible. In this way, unallowable attenuation increases in the optical fiber due to bending or position changes can be avoided.

FIELD OF INVENTION

Between an optical fiber (LB11, LFB12, LFB13) and a surrounding corecovering (AH11, AH12, SB13) of an optical transmission element (OE11 toOE13) there is at least one dry and compressible fixating element (FE11to FE13), which surrounds the optical fiber totally or partially, andwhich exerts a defined contact pressure against the core covering andagainst the optical fiber for fixating the optical fiber in thelongitudinal direction of the transmission element. The fixating elementis further formed and positioned in such a way, that position changes ofthe optical fiber due to bending or elongation are possible. In thisway, unallowable attenuation increases in the optical fiber due tobending or position changes can be avoided.

BACKGROUND OF INVENTION

The present invention concerns an optical transmission element with atleast one optical fiber and with a core covering surrounding the opticalfiber.

Optical transmission elements such as optical cables or optical coresare often installed in such a way, that the cable ends or core ends,respectively, hand down vertically at the connection points. This canlead to the optical fibers in the cable or core, respectively, which areusually positioned in the cable or core, respectively, with a definedexcess length, partially emerging, due to the force of gravity. Anemerging of the optical fibers poses a problem, especially in the areaof connector sleeves, since the fibers being inserted into the connectorsleeves bend sharply and can thus break because of emerging.

A usual method for fixating the optical fibers in an opticaltransmission element is filling the slot with high viscosity,thixotropic or cross-linked filling compound.

Such a filling compound has the disadvantage, that it can run out ordrip out in the case of vertically hanging ends of the transmissionelement. Additionally, contamination and problems with handling canoccur when the filling compound leaks during opening up the transmissionelement during installation.

With dry, unfilled optical cables, swell tapes are often used forsealing the cable against water penetration. They are formed in such away, that they swell during water penetration and thus seal the cable.Such a swelling tape usually does not fill the empty space between theoptical fibers and the surrounding core covering so that the swell tapecannot fixate the fibers.

SUMMARY OF THE INVENTION

It is the objective of the present invention, to provide an opticaltransmission element with at least one optical fiber and a core coveringsurrounding the optical fiber, where the optical fiber is definitelyfixated in the longitudinal direction of the transmission element andwhere unallowable attenuation increases in the optical fiber due tobending or changing lengths of the transmission element are avoided.

The objective is achieved by an optical transmission element accordingto the present invention.

The fixating of the optical fiber in the transmission element isachieved by a dry and compressible fixating element, which is positionedbetween the optical fiber and the core covering. It surrounds theoptical fiber totally or partially and exerts a defined contact pressureagainst the core covering and the optical fiber, so that a certainfixating of the optical fiber along the longitudinal direction of thetransmission is achieved. Since the fixating element is additionallyformed and positioned in such a way, that position changes of theoptical fibers due to bending or elongation are possible, unallowableattenuation increases in the optical fibers due to bending or positionchanges are avoided. Due to the fact, that changes in position to acertain degree are possible because of the compressible structure of thefixating element, the optical fiber, for example, in the form of one ormore optical fibers, has a certain a certain empty space and ability tomove, so that no unallowable attenuation increases occur, for example,during bending of the optical transmission element.

In an advantageous construction of the invention, the fixating elementcontains an elastic foam film or is formed as an elastic foam film. Thefoam preferably contains an elastomer foam, especially polyurethanefoam, polyether foam or polyester foam. By means of the foam film, adefined setting of the contact pressure and the correct frictionrelative to the optical fiber is possible, where, however, certainposition changes of the optical fiber are possible due to the flexibleconstruction of the foam film.

In a further construction of the invention, the fixating elementcontains a fiber-like, fluffy material. Such a material has essentiallysimilar characteristics as the foam film previously described. Forexample, cotton, fiber fill or velvet-like polyester with small densityand high flexibility or good deformation, respectively, can be used. Asthe previously described foam film, such a fixating element also servesadvantageously as crushing protection for the optical fiber.

In another construction of the invention, the fixating element isconstructed in the form of a compressible sealing ring, which is woundaround the optical fiber. The fixating element can also be constructedas a profile conforming to the cross-sectional form of the slot elementand optical fiber. Profiles in the form of a U-profile or slit sealingrings are especially suited for this.

In an especially advantageous construction of the invention, severalseparate fixating elements are positioned along the longitudinaldirection of the transmission element, with gaps in between, which arenot occupied by fixating elements. In the gaps optical fibers can movecomparatively easily during bending of the transmission element, so thatattenuation increases can be prevented. For this, the gapsadvantageously have a larger longitudinal extension than the respectivefixating elements. Because of this, it is also possible, that severaloptical fibers, which are stranded together, can form an almostundisturbed excess length helix in the transmission element. In orderfor the fibers to be able to move easily within at least half a laylength during bending of the transmission element, the longitudinalextension of the respective gaps advantageously amounts to at least onelay length of the respective stranded optical fibers.

In one construction of the invention, several separate fixating elementsare positioned along the longitudinal direction of the transmissionelement on a support film connecting the fixating elements. For creatinga good waterproofing for the transmission element, the support film isformed with swelling ability on at least one side, for example, byproviding it with a swell tape. In this way, very good waterproofing forthe transmission element can be achieved, because the penetrating wateris slowed down at each fixating element and thus it can spread along thelongitudinal direction only very slowly. The free swellable side of thesupport film between the fixating elements can swell undisturbed in theslowly flowing water and quickly seals the empty space between theoptical fibers and the core covering.

For this purpose, a support film with a swell medium dissolving from theribbon can also be used, since the dissolving swell substance cannot beappreciatively washed away due to the severely slowed flow speed. Incase of the swell substance being dissolved by the flowing water, itadheres again to the following fixating element. In this way, thetransmission element is waterproofed after a few centimeters.

For further improvement of the waterproofing of the transmissionelement, the fixating element is mixed with a swellable medium orlaminated with swell tape. For example, the swell substance is insertedin powder form into the gaps between the fixating elements, perhaps intothe foam pores of the foam film or in the gaps in the fiber-like, fluffymaterial, respectively.

A further construction of the fixating element can be a foam film, whichis laminated on one or both sides with a swell film. Swell tapes arepreferably used for this, where the swell substance containing side isdirected towards the foam film. Since the foam filling the empty spacebetween the optical fiber and the transmission element severely breaksthe penetrating water, the water can spread only very slowly along thetransmission element. Thus the swell substance waterproofs the cablealready after a few centimeters. It is also advantageous, that the swellsubstance in the foam or the fiber-like, fluffy material, respectively,adheres well and cannot be washed away.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

FIGS. 1 to 3 depict respective cross-section views of constructions ofan optical transmission element according to the invention.

FIG. 4 is a longitudinal section of a construction of an optical core.

FIG. 5 is a view in perspective of a foam film with a support film.

FIG. 6 is a view in perspective of an optical cable.

FIG. 7 is a longitudinal section of a further construction of an opticalcore.

FIG. 8 is a view in perspective of several foam films on a support film.

FIG. 9 is a view in perspective of an optical cable during manufacture.

FIGS. 10 and 11 are respective views in perspective of furtherconstructions of an optical transmission element according to theinvention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows an optical transmission element OE11 in the form of acable, which contains several optical fibers LF11 in the form of singlefibers. The single fibers LF11 are surrounded by a core covering AH11,where a fixating element FE11 in the form of a compressible foam film ispositioned between the fibers LF11 and the core covering AH11. This foamfilm surrounds the individual fibers almost completely (by theapplication of the foam film around the fibers a slit SL is formed) andexerts a defined contact pressure against the core covering AH11 and theindividual fibers LF11 and thus fixates the fibers in the longitudinaldirection of the cable. Due to the flexible construction of the foamfilm, position changes of the fibers, for example, due to bending orelongation of the cable are made possible. The core covering AH11 issurrounded by a swell tape QV11, which in turn is surrounded by aramidyarns AG11. The cable is enclosed by the cable jacket KM11.

FIG. 2 shows a transmission element OE12, which shows optical fibers inthe form of a fiber ribbon LFB12. A fixating element FE12 in the form ofa foam film is positioned between the core covering AH12 and the fiberribbons LFB12. It fulfills the same function as the foam film accordingto FIG. 1. The core covering AH12 is surrounded by aramid yarns AG12;tension-proof GFK elements ZE12 are embedded in the cable jacket KM12.

FIG. 3 shows a transmission element OE13, which shows an optical fiberLFB13 in the form of a 3×12 fiber bundle. A fixating element FE13 in theform of a foam film is positioned between a steel ribbon SB13 and thefiber bundle LFB13. Tension-proof steel wires ZE13 are embedded in thecable jacket KM13.

In all three examples according to FIGS. 1 to 3, the fixating of thefibers in the cable is done by the respective elastic foam film, whichsurrounds the fibers. The cross-section of the film is measured in sucha way, that the gap between the fibers and the slot surrounding thefibers is completely or nearly completely filled, so that a definedcontact pressure on the fibers and core covering is created. The foamfilm preferably contains an elastomer foam with high friction value suchas, for example, polyurethane foam, polyether foam of polyester foam.Preferably foam films with density of between 10 to 100 kg/m³ are used.The foam of the foam film preferably is formed with open pores.

FIG. 4 shows a longitudinal section of a construction of an optical coreOE1, where the optical fibers LF are stranded together and are disposedwithin the core covering AH with excess length. Between the opticalfibers LF and the core covering AH, a continuous compressible foam filmSF is positioned, which is fastened to a support film TF.

FIG. 5 shows a view in perspective of a foam film SF (i.e.—alongitudinal foam tape), which is positioned on a support film TF. Thesupport film TF is preferably formed as a swell film (i.e.—alongitudinal swell tape). In this way, good waterproofing of the opticaltransmission element can be achieved, since water penetrating is sloweddown at the boundary of the foam film by its swelling.

FIG. 6 shows a view in perspective of an optical cable OE2, whichcontains optical fibers LF surrounded by a foam film SF in a corecovering AH, which is then surrounded by a cable jacket KM. The foamfilm SF is formed around the fibers LF as a tube and is then surroundedby the core covering AH or the cable jacket KM, respectively.

FIG. 7 shows a longitudinally section of a further construction of anoptical core OE3. Here several separate foam films SF1 to SF3 arepositioned in the longitudinal direction of the transmission element,with gaps ZR1 and ZR2 positioned between them, which do not haveapplications of foam. The foam films SF1 to SF3 are arranged on asupport film TF in the longitudinal direction of the transmissionelement. The optical fibers LF are stranded longitudinally and can forma nearly undisturbed excess length helix in the transmission element dueto the gaps ZR1 and ZR2. The gaps ZR1 and ZR2 show a grater longitudinalextension than the respective foam films SF1 to SF3. It preferablyamounts to more than half a lay length of the optical fibers. In thisway, the optical fibers LF can easily move during bending of thetransmission element OE3, whereby attenuation increases due to bendingradii of the optical fibers, which are too small, can be prevented.

For the creation of good waterproofing, the support film TF is formed asa swell film. It is, for example, formed with swell capabilities on theside towards the foam segments. Penetrating water is strongly sloweddown at each of the foam film segments and can therefore spread onlyvery slowly in the longitudinal direction. The swell material positionedfreely between the foam film segments can swell undisturbed in theslowly flowing water and quickly seals the empty space between thefibers LF and the core covering AH. In this connection, swell tapes witha swell substance dissolving from the tape can also be used, since theswell substance can only be washed away due to the greatly diminishedflow speed. Swell substance, which is washed away, can deposit itself oneach of the foam film segments.

FIG. 8 shows a view in perspective of several foam film segments SF1,SF2 on a support film TF. The support film TF is able to swell at leaston the side QA, preferably equipped with a swell tape. The swellableside QS of the support film TF is oriented toward the foam film segmentsSF1, SF2, which are arranged on it. The foam film segments are fastenedto the support film TF in appropriate distances, for example, by meansof gluing.

For especially good waterproofing, the foam films, which in theirnon-waterproof state fill the total empty space between the fibers andtheir protective covering, are displaced by a substance, that swellsduring water penetration. This swell substance can be positioned in thefoam pores in powder form. In a further construction, the respectivefoam film can be laminated on both sides with a swell film. Preferablyswell tapes are used for this purpose, whereby the swell substancecontaining side is oriented toward the foam material of the foam film.The swell substance is advantageously held firmly in the foam and cannotbe washed away. The foam filling the gap strongly slows down penetratingwater, so that it can spread along the transmission element only veryslowly. The swell substance seals the transmission element already aftera few centimeters.

FIG. 9 shows a view in perspective of an optical cable OE4 duringmanufacture. The foam film segments SF1 to SF3 located on the supportfilm TF are formed into a tube around the fibers LF and are surroundedby a core covering AH and a cable jacket KM. The foam films SF1 to SF3and also the foam film SF according to FIG. 6 are a prefabricatedproduct and can be manufactured comparatively economically. Theapparatus expenditure for the manufacture of the cable can therefore bekept comparatively low.

FIG. 10 is a view in perspective of a construction of an opticaltransmission element, where the optical fibers LF are wound by afixating element in the form of a compressible sealing ring RS. Thesealing ring RS supports itself by leaning toward the outside against acore covering, which is not depicted.

FIG. 11 shows a further construction of a transmission element, wherethe fixating element is formed as a profile PF, which conforms to therespective cross-section form of a core covering not depicted and theoptical fiber LFB. The profile PF has the form of a U-profile.

1. An optical transmission element, comprising: at least one opticalfiber; a core covering, the core covering disposed about the at leastone optical fiber, wherein a space is defined by an area disposedbetween the at least one optical fiber and the core covering at across-section of the optical transmission element; and at least onefixating element, the at least one fixating element including a foamtape, the foam tape being disposed between the at least one opticalfiber and the core covering, wherein the at least one fixating elementextends longitudinally along the core covering and the at least onefixating element substantially fills the space between the at least oneoptical fiber and the core covering at one or more cross-sectionalportions of the optical transmission element for coupling the at leastone optical fiber while allowing for position changes of the at leastone optical fiber during bending or elongation of the opticaltransmission element.
 2. The optical transmission element according toclaim 1, wherein the at least one fixating element further includes aswell tape attached to the foam tape, and the swell tape has a swellsubstance and a swell substance side of the swell tape is orientedtoward the foam tape.
 3. The optical transmission element according toclaim 2, wherein the foam tape is selected from the group containing ofan elastomer foam, a polyurethane foam, a polyether foam, and apolyester foam.
 4. The optical transmission element according to claim1, wherein the foam tape has a density between about 10 kg/m³ and about100 kg/m³.
 5. The optical transmission element according to claim 1,wherein the at least one fixating element further includes a swell tape.6. The optical transmission element according to claim 1, wherein thefoam tape has open pores.
 7. The optical transmission element accordingto claim 1, wherein the at least one fixating element is wound about theat least one optical fiber.
 8. The optical transmission elementaccording to claim 1, wherein the at least one fixating element has across-sectional profile that generally conforms with a cross-sectionalprofile of the core covering.
 9. The optical transmission elementaccording to claim 1, wherein the at least one fixating element furtherincludes a support tape and the foam tape includes a plurality of foamtape portions attached to the support tape so that the plurality of foamtape portions are intermittently spaced on the support tape.
 10. Theoptical transmission element according to claim 9, wherein the supporttape is a swell tape.
 11. The optical transmission element according toclaim 9, wherein the at least one optical fiber is longitudinallystranded with a predetermined laylength and the plurality of foam tapeportions having a longitudinal gap between adjacent fixating elements,where the longitudinal gap extends for at least one-half of thepredetermined laylength.
 12. The optical transmission element accordingto claim 1, wherein the optical transmission element includes aplurality of fixating elements.
 13. The optical transmission elementaccording to claim 12, wherein one of the plurality of fixating elementsincludes a swell feature for inhibiting the migration of water along theoptical transmission element.
 14. The optical transmission elementaccording to claim 1, wherein the at least one fixating element contactsa portion of the at least one optical fiber.
 15. The opticaltransmission element according to claim 1, wherein the at least oneoptical fiber is a portion of an optical fiber ribbon and the at leastone fixating element contacts a portion of the optical fiber ribbon. 16.The optical transmission element according to claim 1, wherein the atleast one fixating element further includes a swellable portion forinhibiting the migration of water along the optical transmissionelement.
 17. The optical transmission element according to claim 16,wherein the swellable portion is a portion of a swell tape.
 18. Theoptical transmission element according to claim 1, wherein the opticaltransmission element is a portion of a fiber optic cable, the fiberoptic cable having at least one strength element for carrying a tensileload.
 19. An optical transmission element, comprising: at least oneoptical fiber; a core covering, the core covering disposed about the atleast one optical fiber; and at least one fixating element, the at leastone fixating element includes a foam tape that is attached to a swelltape, the at least one fixating element being disposed between the atleast one optical fiber and the core covering, wherein the at least onefixating element extends longitudinally along the core covering forcoupling the at least one optical fiber while allowing for positionchanges of the at least one optical fiber during bending or elongationof the optical transmission element.
 20. The optical transmissionelement of claim 19, wherein the at least one fixating elementsubstantially fills a space defined by an area disposed between the atleast one optical fiber and the core covering at one or morecross-sectional portions of the optical transmission element.
 21. Theoptical transmission element according to claim 19, wherein the swelltape has a swell substance and a swell substance side of the swell tapeis oriented toward the foam tape.
 22. The optical transmission elementaccording to claim 19, wherein the foam tape is selected from the groupconsisting of an elastomer foam, a polyurethane foam, a polyether foam,and a polyester foam.
 23. The optical transmission element according toclaim 19, wherein the foam tape has a density between about 10 kg/m³ andabout 100 kg/m³.
 24. The optical transmission element according to claim19, wherein the foam tape has open pores.
 25. The optical transmissionelement according to claim 19, wherein at least one fixating element iswound about the at least one optical fiber.
 26. The optical transmissionelement according to claim 19, wherein the at least one fixating elementhas a cross-sectional profile that generally conforms with across-sectional profile of the core covering.
 27. The opticaltransmission element according to claim 19, wherein the foam tapeincludes a plurality of foam tape portions attached to the swell tape sothat the foam tape portions are intermittently spaced on the swell tape.28. The optical transmission element according to claim 19, wherein theat least one fixating element contacts a portion of the at least oneoptical fiber.
 29. The optical transmission element according to claim19, wherein the at least one optical fiber is a portion of an opticalfiber ribbon and the at least one fixating element contacts a portion ofthe optical fiber ribbon.
 30. The optical transmission element accordingto claim 19, wherein the optical transmission element is a portion of afiber optic cable, the fiber optic cable having at least one strengthelement for carrying a tensile load.
 31. An optical transmissionelement, comprising: a plurality of optical fiber ribbons, the opticalfiber ribbons forming a ribbon stack; a core covering, the core coveringdisposed about the ribbon stack, wherein a space is defined by an areadisposed between the ribbon stack and the core covering at across-section; and at least one fixating element, the at least onefixating element includes a foam tape, the at least one fixating elementbeing disposed between the ribbon stack and the core covering and the atleast one fixating element substantially fills the space between theribbon stack and the core covering at one or more cross-sectionalportions of the optical transmission element, wherein the at least onefixating element extends longitudinally along the core covering forcoupling the plurality of optical fiber ribbons while allowing forposition changes of the plurality of optical fiber ribbons duringbending or elongation of the optical transmission element.
 32. Theoptical transmission element according to claim 31, wherein the at leastone fixating element further includes a swell tape.
 33. The opticaltransmission element according to claim 31, wherein the at least onefixating element further includes a swell tape, and the swell tape has aswell substance and a swell substance side of the swell tape is orientedtoward the foam tape.
 34. The optical transmission element according toclaim 31, wherein the foam tape is selected from the group consisting ofan elastomer foam, a polyurethane foam, a polyether foam, and apolyester foam.
 35. The optical transmission element according to claim31, wherein the foam tape has a density between about 10 kg/m³ and about100 kg/m³.
 36. The optical transmission element according to claim 31,wherein the foam tape has open pores.
 37. The optical transmissionelement according to claim 31, wherein the at least one fixating elementhas a cross-sectional profile that generally conforms with across-sectional profile of the core covering.
 38. The opticaltransmission element according to claim 31, wherein the ribbon stack hasa longitudinal strand.
 39. The optical transmission element according toclaim 31, wherein the at least one fixating element includes a swellfeature for inhibiting the migration of water along the opticaltransmission element.
 40. The optical transmission element according toclaim 31, wherein the at least one fixating element contacts a portionof the ribbon stack.
 41. The optical transmission element according toclaim 31, wherein the optical transmission element is a portion of afiber optic cable, the fiber optic cable having at least one strengthelement for carrying a tensile load.